A school campus in the Excelsior district was evacuated early Wednesday morning after school officials received a bomb threat just before class began.

At about 7:45 a.m. the secretary for the June Jordan School for Equity received a phone call reporting a bomb threat to the school, according to police Sgt. Steve Mannina. The principal of the school called the San Francisco Police Department and alerted them to the threat.

“I can’t give you the specifics of what the caller said … from what I understand this was before any students arrived at the school,” Mannina said.

About 250 students who attend the high school on campus and another 200 who attend the adjoining middle school were evacuated from the site as they arrived, according to Mannina. Gentle Blythe, the director of public outreach for the San Francisco Unified School District, said police took the students to an area deemed far enough away from the school that it was safe.

“[Students] have procedures for evacuating,” she said. “They go in orderly lines [and] they have to remain in lines. We take the lead from the police.”

Two police dogs searched the campus for about two hours before determining there was no threat, according to Mannina. He said the search took longer than most bomb threats because the campus is large. Students returned to the school about 10:05 a.m., according to Mannina.

Blythe said bomb threats against schools in The City do not happen often, but when they do, the district works closely with the Police Department.

“The answer is that it does happen and fortunately we have found that the bomb threat has never been substantiated,” she said. “Sometimes they are made by students that are playing a practical joke.”